This invention relates to a multi-pipe pneumatic conveyor system wherein particulate material is transported through a plurality of parallel pipes by means of a high velocity airstream.
A pneumatic conveyor system having a main pipe and a plurality of parallel branch pipes is well known in the art. In such a system, the airflow or air volume through each branch pipe is initially set to a predetermined value by adjusting a damper inserted intermediate the pipe. The system is operated with the damper fixed. The amount of particulate solids to be transported through each branch pipe actually varies over a wide range and this variation works a change in airflow through each pipe. An empirical analysis is previously made to determine a sufficient airflow to provide an air velocity capable of pneumatically transporting particulate solids at the maximum particulate-to-air ratio which is expected to occur in each pipe before the damper is set so as to establish the predetermined airflow. Accordingly, the predetermined airflow is considerably larger than the airflow required for the normal operation where the mixing ratios are uniform in all the branch pipes. The actual mixing ratio in each branch pipe is considerably lower than the maximum expected mixing ratio so that an excess of the air volume flows in vain, increasing power consumption and pipe wear. Since the blower must have an excessive capacity to provide an excessive airflow, not only initial investment, but also operating cost are increased. Furthermore, if the airflow through one branch pipe is extremely increased, the airflow through each of the remaining branch pipes is relatively reduced, and then particulate solids can stagnate in the pipes with increasing particulate-to-air ratios and in the worst case, choke one or more pipes. As described above, the conventional pneumatic conveyor system has the shortcomings that the designed capacity is excessive and troubles often occur.
It is, therefore, an object of the present invention to provide a pneumatic conveyor system wherein the airflow through each branch pipe is kept constant to ensure stable operation.
It is another object of the present invention to provide a controlled pneumatic conveyor system which is operated at an optimum air velocity.
It is a further object of the present invention to reduce the initial investment and operating cost of a pneumatic conveyor system.